The problem was at the beginning.
What I did:
1. First, create your popup or another way you want to use the hustle plugin.
2. Hustle plugging > integrations > add Mailchimp to connected apps // here you won’t have the option to choose the list you want.
3. Then, Hustle plugin > popup (I choose popup because is from where I capture emails) > then
4. A new vertical menu there, choose > integrations > in the applications (and active apps), MailChimp should be there. Go and edit the list you want.
Then, test it and wait a few minutes, because it should be working.
I hope this helps.
Cristian